1. Field of the Invention
The present invention relates generally to a Multiple-Input Multiple-Output (MIMO) communication system and more particularly to a feedback method for multiuser MIMO communication system.
2. Description of the Related Art
Multiple-Input Multiple-Output (MIMO) systems have been one of key techniques to achieve high rate and high reliability over wireless channels. Channel information can be exploited at the transmitter if feedback channel is available. In practical systems, the limited feedback channel capacity is allowed and in a multiuser channel environment the design methodology of exploiting the partial channel knowledge at the transmitter is necessary. Recently, multiuser diversity has been investigated for high data throughput in multiuser communications, where a packet is scheduled to a user who has the highest instantaneous Signal-to-Noise Ratio (SNR). Prior work on multiuser diversity did not consider the full exploitation of user diversity when each transmit antenna is assigned for different users. Thus, in multiuser MIMO systems the limited feedback information and user diversity should be considered at the same time to design transmit preprocessing techniques (i.e. transmit preceding).
However, previous precoder design researchers have been focused on a point-to-point communication, and hence user scheduling has been separately dealt with. Accordingly, it is required to implement a finite rate feedback scheme for a multiuser MIMO transmission in consideration of user selection diversity.